Fix: compile error in 88aeed5

MobileLibrary/psi/psi.go

@@ -28,7 +28,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"strings"
 	"sync"
 
 	"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon"